Number portability using enhanced routing table

ABSTRACT

A method of providing number portability for the treatment of calls from a calling party to a specific number of a called party is disclosed. Once the dialed digits are received at a switching office serving the calling party, a determination is made of whether the call is directed to a portable number. In a first embodiment, if the call is directed to a portable number, a TCAP query is launched from the originating office to an SCP. At the SCP, the dialed digits are translated to obtain new routing information. The new routing information, which is returned to the originating office is used to create an Initial Address Message (IAM) containing the calling and called party&#39;s numbers to enable said call to reach said terminating office associated with the new routing information. In a second embodiment, the new routing information is obtained from a directory number table resident at the originating office. If the dialed digits contain an area code indicative of a toll call, the originating office forwards the call directly to a tandem exchange, where the determination is made of whether the dialed digits are associated with a portable number.

SUMMARY OF THE INVENTION

This invention relates to telephone networks, but more particularly, toa method and system for providing number portability using IN and switchbased database queries.

BACKGROUND OF THE INVENTION

Although efforts are being made to solve some of today's networktransparency constraints, the solutions offered are still constrained bythe rigid rules of today's North American Numbering Plan (NANP) and thearchitecture which supports it. That is, each telephone subscriber has anumber in the NXX-NXX-XXXX format, where N represents a digit from 2-9and X represents a digit from 0-9. The first group of three digitsindicates the area code or NPA of the subscriber, the second group ofthree digits indicates a switching exchange or service switching pointto which the subscriber is connected, and the last four digits indicatesthe address of the subscriber within the service switching point. Digits0 and 1 are of course not available as the first digit (N) to allowoperator and long distance services.

With the large increase in telephone devices of one sort or another, anequivalent increase in the demand of telephone numbers has been created.For example, 15 years ago, most telephone numbers were used for fixedPlain Ordinary Telephone Service (POTS) devices. Today, more and moreusers make use of several devices, such as cellular telephones, pagers,fax machines, modems, etc. This demand has placed a large impact on thepool of numbers available for customers. In some instances, ametropolitan area which used to be served by one area code, now requiresseveral. The problem is of course compounded by the need to assign newtelephone numbers to subscribers which move from one region to another.In addition, in the future, numbers must be portable between competingnetwork carriers, namely between the Incumbent Local Exchange Carriers(ILEC) and Competitive Local Exchange Carriers (CLEC).

The same applies to competition between toll carriers, which isespecially fierce to capture business customers who have locations whichare connected via toll lines.

Generally, the customer is interested in forming a seamlesscommunication network in terms of feature operation, and dialingpatterns. It also would like its network to be transparent to callingclients and customers, with calls easily covered, routed and transferredthroughout their network as though they were at a single location.Number portability therefore becomes important to them, not only withintheir private network, but externally as well.

The customer's ability to select an inter-LATA or toll carrier is madepossible by a Regulation called equal access (EA). Equal access is anoperating company tariff which provides a given subscriber access thatis equal in type and quality to every inter-LATA carrier. Each IEC has adialing arrangement, call-screening technique, routing procedure,billing record, and signalling protocol are required to implement the EAenvironment.

The EA concept originated in the United States with the modified finaljudgment (MFJ) of 1982 in which AT&T lost its long-distance monopoly andwas also required to divest itself of the Bell operating companies(BOCs). This divestiture action resulted in the formation of sevenregional holding companies, each comprised of a number of the originalBOCs. Manufacturers have implemented the EA concept according to theregulatory requirements of the 1982 MFJ. The United States EA concept isbuilt on geo-politically defined local access and transport areas(LATAs). A LATA is a fixed non-overlapping geographic area determined atthe time of the MFJ ruling. Telecommunication services within a LATA,including local and toll calls within a LATA, are carried by Belloperating companies. Inter-LATA traffic must be carried by an inter-LATAcarrier (IC). Today, intra-LATA competition is now allowed in the UnitedStates. That is, subscribers have the capability of selecting analternate intra-LATA carrier for intra-LATA calls as well as aninter-LATA carrier for inter-LATA calls. The BOC must transferinter-LATA traffic to the IC directly from the end office (EO) or via anintermediate switch called an access tandem (AT). The physical locationof an IC within a LATA is referred to as the point of presence (POP).

As indicated above, regulators have requested that once implemented,number portability should be available across competing networks.Unfortunately, network facilitators have been unsuccessfully researchingoptions for delivering a service in which telephone numbers are not tiedto equipment locations.

New telephone networks with Advanced Intelligent Network (AIN) conceptshave been proposed to support faster development of new services througha network architecture in which network functions and interfaces arestandardized providing greater independence between service software andtechnology.

One service application which makes use of AIN technology for separatingdialing from physical routing is Local Number Portability (LNP). Theapplications are being examined by the Information Industry LiaisonCommittee (IILC) for extension of LNP concepts. Many options have beendiscussed and are being investigated. The options to route based onnetwork number ownership fall short, in the sense that they imposevarious limitations, and are at this time unworkable.

An attempt to provide number portability for a private network isoffered in U.S. Pat. No. 4,754,479, which issued to Bicknell et al. Inthis patent, an arrangement is disclosed for providing station numberportability to stations ported from an original switching node to a newswitching node which allows the ported station to maintain its originalassigned station number. Bicknell et al. is able to achieve this featureby providing a data base, common to each and every switching nodelocated within a portability cluster. Thus, when a calling partyattempts to reach a called party, which is now served by a new switchingnode, the switching node serving the calling party will be able toidentify, from the common database, that the called party is now beingserved by a new switching node and accordingly route the call to thatnew switching node.

Although Bicknell et al. offer that their service could be expanded toprovide a network wide service, they confess that an extensive commondatabase, listing station number and switch associations would berequired and that such a large database could only be implemented ifspace and economic constraints were removed.

The current direction for network evolution is to remove intelligencefrom the telephone exchange using database query procedures to increasenetwork flexibility. Where initial decisions can be made for launching aquery to a database, increased flexibility can be easily obtained,usually with reduced costs. However, the costs increase dramaticallywhen all calls from a specific exchange require this procedure. Forexample, costs associated with the database query implementationinclude:

AIN and/or vendor license charges (usually on a per dip basis);

Increase in exchange CPU requirements (factor of 2-5 per call);

Augment of the signalling network;

Database infrastructure required to support queries; and

Database updates to keep all systems current.

Number portability requires the treatment of all calls to a specificnumber irrespective of the point of origin, making the terminatingswitch the most logical location to control the call. Initially, thisconcept seemed to present an inexpensive option for allowingportability, but it was soon realized that as the numbers increase, manyadditional circuits would be required. At this point, release linktrunks can be employed to reduce the connections, but this requires acommon protocol and significant interconnection development.

Most solutions carry significant development requirements and it istherefore important to choose the option which can support therequirements over the long term.

Two options are the most widely recognized and popular at present. Thefirst is to use AIN technology to use a query and response procedure foreach call to query a database to establish number ownership. The secondoption is that of Terminating Switch Routing. This proposal consists ofthe routing of calls using the existing NANP to the expected terminatingswitch location where, when numbers are owned by another network, callsare then route advanced to that network. In some cases, release linktrunks are envisioned to reduce the number of circuits required.

Some problems still exist in implementing these proposed methods,including flash cuts, calls being routed several times between networksand inefficient routing schemes. In addition, the solutions proposedabove, are meant to make use of AIN technology. Although AIN isconsidered a subset of Intelligent Networks (IN), number portabilityshould not be limited to AIN networks only.

A need therefore exists for providing a mechanism to take advantage ofthese various methods while providing the flexibility to eliminatesingle option constraints.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide numberportability which overcomes the aforementioned problems.

Another object of the present invention is to provide a method ofrouting calls between networks with ported numbers while making use ofexisting facilities, minimizing call routing complexities and costs.

Yet another object of the present invention is to provide numberportability such that calls to ported numbers are identified by usingthe public network's switch hierarchy.

Yet another object of the present invention is to provide numberportability wherein ported calls within a local area are identifiedlocally, whereas calls to ported numbers which are routed external ofthe calling area are identified externally thereof.

Accordingly, a first aspect of the invention is to provide in atelephone network having a number of telephone switching officesequipped with SSPs (Service Switching Points) operating with IN(Intelligent Network) application software, a method of providing numberportability for the treatment of calls from a calling party to aportable number of a called party, comprising the steps of:

a) receiving digits dialed by said calling party at an exchange in acall path determined by the dialed digits;

b) determining at a first directory number database in the call pathdetermined by the dialed digits whether the dialed digits are associatedwith a ported number;

c) determining at a second directory number database a routing optionfor the dialed digits, if the dialed digits are determined at step b) tobe associated with a ported number;

d) establishing a signalling path from said exchange in the call pathdetermined by the dialed digits to a terminating exchange associatedwith the routing option by creating an Initial Address Message (IAM)according to said routing option; and

e) receiving said Initial Address Message (IAM) at said terminatingexchange to enable the call to reach the called party.

A second aspect of the invention is to provide in a telephone networkhaving a number of telephone switching offices equipped with SSPs(Service Switching Points) operating with IN (Intelligent Network)application software a system for providing number portability for thetreatment of calls from a calling party to a portable number of a calledparty, comprising:

a) a first switching office for receiving digits dialed by said callingparty;

b) a second switching office connected to said first switching officevia a signalling path established for routing a call associated with thedialed digits;

c) first directory number database means, for determining whether saiddialed digits are associated with a portable number;

d) second directory number database means for providing a routingoption, if said dialed digits are determined to be associated with aportable number and for translating said dialed digits to provide a newrouting option, said first office creating an Initial Address Message(IAM) which contains said new routing option, such that when said newrouting option is received at said second office said terminating officecan enable said call to reach said called party.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to impart full understanding of the manner in which this objectand others are attained in accordance with the present invention,preferred embodiments thereof will be described hereinafter withreference to the accompanying drawings wherein:

FIG. 1 is a diagram illustrating generally the basic signalling callflow between an originating and a terminating office;

FIGS. 2a and 2b are diagrams illustrating signalling call flow scenariosaccording to a first and second embodiment of the present invention;

FIGS. 3a and 3b are diagrams illustrating signalling call flow scenariosaccording to a third and fourth embodiment of the present invention;

FIGS. 4a and 4b are diagrams illustrating database tables for use withthe present invention;

FIG. 5 is a diagram illustrating a typical network which can make use ofthe method of the present invention; and

FIG. 6 is a diagram illustrating a call scenario for a network havingaccess to a CLEC.

In the following description and the drawings, the same referencenumerals will refer to the same structural elements.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In order to lighten the following description, the following acronymswill be used:

ACM: Address Complete Message;

AIN: Advanced Intelligent Network;

ANM: Answer Message;

CCS7: SS7 network signalling;

CLEC: Competing Local Exchange Carrier;

LATA: Local Access Transport Area;

IAM: Initial Address Message;

IEC: Inter Exchange Carrier;

ILEC: Incumbent Local Exchange Carrier

IN: Intelligent Network;

ISDN: Integrated Services Digital Network;

ISUP: ISDN User Part;

POTS: Plain Ordinary Telephone System

PSTN: Public Switching Telephone Network;

REL: Release Message;

RLC Release Complete;

SCP: Signalling Control Point;

SSP: Service Switching Point;

STP: Signalling Transfer Point;

SUS: Suspend Message;

TCAP: Transaction Capabilities Application Part.

As indicated above, AIN is considered a subset of IN. However, for thepurpose of the present invention, IN will be used hereinafter, eventhough the solutions offered here are applicable to AIN as well.

A typical SS7 network consists of signalling links and nodes. SS7 nodesare referred to as signalling points (SP) and are interconnected bysignalling links. Each SS7 signalling node is assigned a unique pointcode, serving as the network address for message routing. SS7 signallingnodes include signalling Points (SP), service switching points (SSP),service control points (SCP) and signal transfer points (STP).

Signalling points (SP) are capable of sending and receiving SS7 messageswith other SS7-equipped telephone offices, and routing calls based onthe information exchanged. Incoming messages are formatted andtransferred to the relevant processing function in the switch. Outgoingmessages are transmitted over the signalling links.

Service switching points (SSPs) are Signalling Points (SP) furtherequipped to halt call progress, launch an SS7 query to obtain additionalrouting information from an SCP, and then route or treat the call basedon the information received in the SCP's response. SSPs interact withdatabases to provide services and routing.

Service control points (SCP) are often referred to as SS7 servicesdatabases. One or more SCPs can serve as a central intelligence point inthe network for enhancing how and if calls are to be routed through thenet work. Queries and responses to and from the SCP are carried over SS7signalling links in the form of packet messages.

Signal transfer points (STP), are special SS7 nodes which provide amessage switching function between other nodes and a SS7 network. Actingas a packet switch, it examines incoming messages and then routes themover the appropriate signalling link to the proper destination switchingoffices and databases. In this particular function, it supportsend-to-end signalling, i.e. in transit (local, tandem and toll)connections, required for transaction messaging used for specialservices. Unlike other SS7 nodes, the STP does not generally act as asource or sink for SS7 messages.

Referring now to FIG. 1, we have shown a flow diagram which is used forproviding an understanding of ISUP (Integrated Services Digital Network(ISDN) User Part) call progression. Signal ling Transfer Points (STPs)have been shown but are usually transparent to ISUP signalling.

The message purposes are defined as follows:

Initial Address Message 15 (IAM): Indicates a request to each subsequentexchange for call set-up and to reserve the indicated trunk. Callconnection will not be completed until the status is returned indicatingth e call path has been confirmed and the dialed number exists and isidle. The IAM contains information about both the calling and calledparties.

Address Complete Message 16 (ACM): Indicates to the originating exchangethat the call path has been confirmed and the dialed address exists andis idle.

Answer Message 17 (ANM): Returned by the terminating exchange once thecall has been answered. Both directions of the call path 18 areestablished at this time.

Release Message 19 (REL): Sent by the originating office to indicatethat the originating party has terminated the call.

Release Complete 20 (RLC): Indication from the terminating exchange thatthe release message has been received and all connections have beenterminated. The RLC can be considered as an acknowledgment of a RELmessage and the circuit being taken down.

In the call scenario of FIG. 1, the signalling call flow is illustratedfor call set-up and take-down of a call between originating office 10and terminating office 11, via tandem exchange or intermediate office12. After the calling party has picked up the receiver, received a dialtone and entered digits, dialed digits are received at the originatingswitch 10. The first message sent during ISUP signalling call set up isan Initial Address Message 15 (IAM), which is created and sent from anoriginating office 10 to a tandem exchange 12 and re-created at tandemexchange 12 and forwarded to terminating office 11. The STP pairs 13 and14, as indicated above, have been shown but are usually transparent toISUP signalling. The IAM message 15 passes information about the call toall subsequent offices in the path. The IAM reserves a voice path whileverifying the availability of the destination station, at the far end,i.e. terminating office 11. An Address Complete Message (ACM) 16 thensends confirmation that the dialed address both exists and is idle.Where the far end is available, a call path is established. Once thecalled party answers, an answer message (ANM) 17 is then returned to theoriginating office 10 and the conversation 18 then begins.

Call termination can be initiated from either the originating office 10or the terminating office 11. Most ISUP protocols make use of releasemessages in either direction, for example, REL message 19 of FIG. 1. Arelease complete message (RLC) 20 is then returned, in this case, fromthe terminating office 11 to the originating office 10, indicating thatall circuits have been returned to the available resource pool.

As indicated above, the present invention makes use of the switchhierarchy which exists in most public networks in order to provide localnumber portability. That is, as a call progresses through its path tothe called party, the identification of whether the dialed number isported, is done as the call is routed from the originating switch to thenew terminating switch where the called station is now ported. The term`ported` is used to indicate that a connection or `port` for the calledstation exist at that switch. Thus, before number portability wasestablished, the location of a called station or where it was ported wasbased on it's NPA-NXX-XXXX numbering plan. A called station could belocated in a network based on this numbering plan. However, with numberportability, the identification of the switch on which a called stationis ported can no longer be established by simply routing the call basedon the station's directory number.

With the present invention, the identification of whether the dialednumber is ported, is done as the call is routed from the originatingswitch to the new terminating switch where the called station is nowported. This is done regardless of whether the called party is servedlocally, externally of the calling area, by the ILEC or a CLEC.

In order to route a call, a table is required on each telephone exchangein the network to permit a binary search to be performed to determinewhether the North American Numbering Plan (NANP) can be used to routethe call. Such a table is shown in FIG. 4a and will be described furtherbelow.

With the present invention, when the destination numbers are owned bythe ILEC, the call is routed using standard NANP translations. On theother hand, the determination of whether the destination number isflagged as unique, i.e. is a portable number, is made from an enhancedtable located at a switching node along the call path. Once thedestination number is flagged as unique at the enhanced table, a routingoption is provided to enable the call to reach its final destination. Inone embodiment, the routing option is provided in response to a query toan external database. This is illustrated with reference to FIGS. 2a and3a.

The call scenario illustrated in FIG. 2a, is based on calls made locallywherein no toll charges apply. The originating office 30 serving thecalling party in the (760) exchange, terminating office 31 serving the(780) exchange and the switching office 32 serving the (789) exchange,each make use of an updated directory number table 33 located in aninternal directory number database 34, to enable the routing of anincoming call. The updated tables show that toll calls, i.e. those withan NPA prefix 35, should be routed via CIC 010 trunk 36 serving a tollor tandem exchange (not shown). Calls with the (789) prefix are routedvia the CIC (789) trunk 37 to the (789) switching office 32, whereasthose with a (780) prefix are routed via the CIC (780) trunk 38 to the(780) switching office 31. The updated table 33 also includes a list ofstation numbers 40 identified as being portable. In the example of FIG.2a, the station having telephone number 789-2000 has been moved to a newlocation in the network which is normally served by a switching office31 serving the (780) exchange. Therefore, the updated table 33 indicatesthat calls directed to portable numbers should launch a query to the SCP41. A TCAP message 42 is thus formulated at the originating switch 30and then launched to the SCP 41, via STP 43. At the SCP, a determinationis made of how and where the call should be routed for this portablenumber. A table, such as shown in FIG. 4b, provides the routinginformation. In the present example, a response 44 would be sent backfrom the SCP to the originating switch 30 indicating that the call is tobe routed to the CIC (780) trunk 38 and not the CIC (789) trunk 37. Atthe originating office 30, an IAM is formulated containing the requiredinformation to establish a call path to termination office 31.

In the call scenario of FIG. 2b, a determination of how and where thecall should be routed for the portable number is made at the updatedtable. Thus, instead of launching a query to a database for portablenumbers, the updated directory table would be further enhanced with theactual routing option normally provided by the external database. Forexample, the routing option for the dialed number would immediatelyindicate that the call is to be routed to the CIC (780) trunk 38. AnInitial Address Message (IAM) representative of this routing optionwould be created at the originating office 30 to establish a call withterminating office 31 where the called station is now ported.

In the call scenario shown in FIGS. 3a and 3b, a calling party 45 isattempting to reach a station 46 located in an area where toll chargesapply. In this example, the area is situated in a different NPA, i.e.wherein the area code of the called party differs from the area code ofthe calling party. Therefore, since the originating office 47 identifiesthat the dialed number is a toll call, an IAM 48 is formulated at theoriginating switch 47 and forwarded to NPA tandem office 50. The IAMmessage 48 is sent as a result of the number translation that took placeat the table 49 of the originating switch 47. At the tandem office 50,the IAM message 48 is interpreted and the dialed number is identified tobe associated with a portable number from a table 51, similar to theupdated table 49 at the originating switch 47. A TCAP query 52 cantherefore be launched from the tandem office 50 to the SCP 41, via theSTP 43. At the SCP 41, a determination is made of how the call is to berouted. In this example, the response 53 to the SCP query 52 contains anew routing option indicative of a trunk to route the call to the newterminating office 31 now serving the ported called party. Once aresponse 53 from the SCP 41 is received, a new IAM 54 is forwarded tothe new terminating office 31. In this example, the terminating office31 serves those telephone numbers having (780) exchanges. Theterminating office 31 routes the call to called station 46 and anacknowledgment message 55 is returned to the originating office 47,indicating that a conversation path 56 can be established.

In the call scenario of FIG. 3b, a determination of how and where thecall should be routed for the ported number is made at the updatedtable. Thus, instead of launching a query to a database for portablenumbers, the updated directory table would be further enhanced with theactual routing option normally provided by the external database. Forexample, the routing option for the dialed number would immediatelyindicate that the call is to be routed to the CIC (780) trunk 38connecting tandem office 50 to the new terminating office 31 of thecalled party 46.

Thus, with the method of the present invention, instead of forwarding atoll call via the tandem office to the switching office which wouldnormally serve the call, if the number was not portable, the tandemoffice is provided with an updated table enabling it to determine atthat point in the call path, whether the call is directed to a portablenumber and, from a database query, which switching office is now servingthe called party.

As indicated above, portable numbers are anticipated to be numberscurrently assigned to a specific office in the North American NumberingPlan (NANP). Where blocks of numbers are assigned to alternate serviceproviders, they would be considered within the NANP and therefore wouldbe routed directly based on the assigned block. Therefore, with eachportable number, the terminating exchange must be updated with theinformation that the number is now portable. With the method of thepresent invention, number portability is implemented by augmenting theexisting Directory Number table with a field to indicate the number isportable. This is shown in FIG. 4a. The internal database 60 at theterminating office is provided with a customer profile which includes,amongst others, a directory number field 61 and a portability field 62.This table can of course be an exclusion table, wherein the absence ofthe dialed DN indicates number portability. The directory number table65 of FIG. 4b can either be used at the SCP 41 or be resident at theswitching office to determine from the portable number field 66 acorresponding routing option from field 67.

The enhanced table can include a unique designation for portable numberswithin the incumbent LEC network, portable numbers in a competitivelocal exchange carrier (CLEC) network, and numbers which have moved intoanother area such as an NPA. Examples of these conditions areillustrated in the table below.

    ______________________________________                                                Examples of Routing Options                                           Dialed Number                                                                           Portable Number                                                                            by Database Query                                      ______________________________________                                        383-1234  Yes          Trunk and Switch ID                                    599-7325             Yes                                                                                       Carrier ID Code                              604-687-1234                                                                                   No               613-788-3456 (Route Advance)                613-793-6543                                                                                   Yes             613-538-5791 (CLEC Number)                   705-429-3453                                                                                   Yes             416-594-7325 (changed NPA)                   ______________________________________                                    

The tables need not be identical on each exchange. Thus tables can beupdated uniquely and need not be duplicated or replicated across allexchanges by metropolitan area, local area, region, LATAs or any otherarea. This reduces the size of each table which becomes important onceportable number penetration is significant. Number ranges will also bean important mechanism for reducing search time and table size.

This is illustrated with reference to the network diagram of FIG. 5. Inthis figure, a geographic area 650 is shown comprised of multipleregions, each of which is served by one or more switching centraloffices (COs). Those switching offices that share a signalling trunk,also share each others list of portable numbers. For example, theswitching office 651 of region A shares a list of local portable numberswith the switching office 652 of region B, as well as the switchingoffices of regions G, X and Y. However, the list of portable numbers ofthe switching office 651 of region A is not available to the switchingoffice 653 of region D, since those two offices do not, share a commonsignalling trunk. Thus, if a calling party 654 in region A attempts toreach a station 655 from region D, the call path will be established viathe tandem office 656. Since the tandem office 656 shares a signallingtrunk with the switching office 653 of region D, it will be able toidentify, from it's directory number database, that the dialed digitssent from region A are directed to a ported number now identified withregion D.

A call scenario making use of the network illustrated in FIG. 5, isshown in FIG. 6. In the network of FIG. 6, local exchanges LS21, LS22and CLEC21 share a list of ported numbers, since they are connected andshare at least one common signalling trunk. Similarly, local exchangesLS11, LS12, LS13 and CLEC11, also share a list of ported numbers, forthe same reasons. Thus, calls made to locally ported numbers will berouted based on information obtained at a local switching office servingthe called party.

However, if a calling party from say, local switching office LS21 dialsa number normally associated with one of the local exchanges in groupLS11, LS12, LS13 or CLEC 11, the switching office LS21 will direct thecall via a toll exchange to enable the routing of the call. Once thecall an IAM address message is received at the receiving toll exchange,a search is made at that exchange to determine whether the called numberis portable. If ported, the toll exchange will either query an externaldatabase or one resident on the exchange to determine the routing optionfor that call. The call can then be completed as indicated before.

Therefore, a certain level of control over the size of the databaserequired, can be obtained by limiting how many switching offices will besharing a list of ported numbers.

This becomes relatively important in achieving network wide LNP, withoutbeing limited by the hardware constraints of the existing networks.

This solution therefore provides better use of the network's resourcesand at the same time, reduces the costs associated with providing numberportability.

Variations of the particular embodiment herewith described will beobvious to one skilled in the art, and accordingly the embodiment is tobe taken as illustrative rather than limitive, the true scope of theinvention being set out in the appended claims.

We claim:
 1. A method of providing network-wide number portablility forthe treatment of calls in a telephone network of telephone exchangesequipped with SSPs (Service Switching Points) operating with IN(Intelligent Network) application software, comprising:a) providing atable at each telephone exchange in the network in which any number in anumbering plan supported by the network can be a ported number to permita search to be performed to determine, each time a called numberassociated with a call is received at the telephone exchange, whetherthe called number is a ported number for which the telephone exchangemust obtain routing information by searching the table for the callednumber; b) providing at least one database, the at least one databasecollectively containing a routing option for each ported number in thenetwork; and c) when the table at a telephone exchange in the networkindicates that a called number is a ported number, obtaining a routingoption from the at least one database to enable the call to reach itsfinal destination.
 2. A method of providing network-wide numberportability as claimed it claim 1 wherein step c) includes steps of:d)querying a first database local to the telephone exchange when the tableat the telephone exchange indicates that a called number is a portednumber; and e) launching a query to a second database at a ServiceControl Point (SCP) in response to an instruction in the first database,in order to obtain a routing option for the call.
 3. A method ofproviding network-wide number portablility as claimed claim 1 whereinthe table at each telephone exchange in the network permits a binarysearch to be performed to determine whether the called number is aported number.
 4. A method of providing network-wide number portablilityas claimed in claim 1 wherein the tables are not identical on eachtelephone exchange.
 5. A method of providing network-wide numberportablility as claimed in claim 1 wherein the at least one databaseincludes a local database at each telephone exchange, the local databasecontaining a routing option for each ported number in the table of thetelephone exchange.
 6. A method of providing network-wide numberportablility as claimed in claim 1 wherein the at least one databaseincludes a database located at a Service Control Point (SCP) in thenetwork, the SCP containing routing options for the ported numbers in aplurality of tables in telephone exchanges in the network.
 7. A methodof providing network-wide number portablility as claimed in claim 1wherein the routing option is a telephone number, and the called numberis replaced with the routing option.
 8. A system for providingnetwork-wide number portability for the treatment of calls in atelephone network of telephone exchange equipped with SSPs (ServiceSwitching Points) operating with IN (Intelligent Network) applicationsoftware, comprising:a table at each of the telephone exchanges in thenetwork in which any telephone number in a numbering plan supported bythe network can be a ported number, each table adapted to enable asearch to determine whether a called number associated with a callreceived at a telephone exchange is a ported number for which theexchange must obtain routing information, each telephone exchangeadapted to execute the search to locate the called number each time acalled number is received at the telephone exchange; and at least onedatabase, the at least one database collectively containing routinginformation for each ported number in the table at each telephoneexchange.
 9. A system for providing network-wide number portability asclaimed in claim 8 wherein the at least one database is located in eachtelephone exchange and contains routing information for at least eachported number in the table at the telephone exchange.
 10. A system forproviding network-wide number portability as claimed in claim 8 whereina one of the at least one database is located at a Service Control Point(SCP) in the network, the database located at the SCP including routinginformation for ported numbers listed in a plurality of the tables. 11.A system for providing network-wide number portability as claimed inclaim 9 wherein the one of the at least one database at the telephoneexchange contains an instruction for directing toll calls to a tandemtelephone exchange in the network, andon identifying a called numberassociated with a toll call as a ported number using the table at thetandem exchange, the tandem exchange sends a query to the SCP to obtainrouting information for forwarding the call to a final destination. 12.A system for providing network-wide number portability as claimed inclaim 9 wherein the one of the at least one database at the telephoneexchange contains routing information far directing toll calls to atandem telephone exchange in the network, andon identifying a callednumber associated with a toll call as a ported number using the table atthe tandem exchange, the tandem exchange searches the one database toobtain routing information for forwarding the call to a finaldestination.
 13. A method of using number portability enhanced routingtables, comprising:a) receiving a called number associated with a callat a telephone exchange in a network in which any telephone number canbe a portable number; b) determining, each time step (a) arises, whetherthe called number is a ported number, the step of determining takingplace by performing a search of a table at the telephone exchange in thenetwork to locate the called number; and c) obtaining from at least onedatabase, in response to determining that the called number is a portednumber as a result of step (b), a routing option for each ported numberin the network to enable the call to reach a final destination in thenetwork, the at least one database collectively containing the routingoption for each ported number in the network.
 14. A method of usingnumber portability enhanced routing tables as claimed in 13, whereinstep (c) includes the steps of:(d) querying a first database local tothe telephone exchange for an instruction in response to determiningthat the called number is a ported number in step (b); and (e) obtainingfrom a second database at a Service Control Point (SCP), based on theinstruction in step (d), the routing option for the call.
 15. A methodof using number portability enhanced routing tables as claimed in 13,further comprising replacing the called number with the routing option,the routing option being another telephone number.
 16. A method of usingnumber portability enhanced routing tables as claimed in 13, wherein thecall is a toll call, the telephone exchange is a tandem exchange, andfurther comprising:f) identifying the called number associated with thetoll call as the ported number after searching the table for the callednumber at the tandem exchange; g) directing, each time the called numberis identified as the ported number pursuant to step (f), the toll callto the final destination in the network.
 17. A method of using numberportability enhanced routing tables, comprising:a) receiving a callednumber associated with a call at one of a plurality of telephoneexchanges in a network in which any number in a number plan supported bythe network can be a ported number; b) determining, each time step (a)arises, whether the called number is a ported number, the step ofdetermining taking place by performing a search of a table at thetelephone exchange in the network to locate the called number; and c)obtaining from at least one database, in response to determining thatthe called number is a ported number from step (b), routing informationfor each ported number in the network, the at least one databasecollectively containing routing information for each ported number inthe network.
 18. A method of using number portability enhanced routingtables as claimed in 17, wherein the call is a toll call, the telephoneexchange is a tandem exchange, and further comprising:d) directing oneof a plurality of toll calls to the tandem telephone exchange in thenetwork, the step of directing taking place pursuant to an instructionfrom the at least one database at the telephone exchange in the network;e) identifying the called number associated with the toll call as theported number, the step of identifying taking place after searching thetable to locate the called number at the tandem exchange; f) obtainingrouting information from at least one database, the step of obtainingtaking place by the tandem exchange sending a query to the SCP; g)forwarding the called number, identified in step (e), based on the queryin step (f), to a final destination.